1. Field of the Invention
The present invention generally relates to a powder container apparatus for an image forming apparatus, such as copy machines, facsimiles, and printers, and to an image forming apparatus equipped with such a powder container apparatus.
2. Description of the Related Art
Image forming apparatuses having image carriers, such as a photosensitive body or an intermediate transfer body, typically also include a cleaning device for collecting residual toner on the image carrier. The waste toner collected by the cleaning device is usually sent to a waste toner container provided within the main body of the image forming apparatus. Such a waste toner container is typically detachable from the apparatus main body of the apparatus, so that, when full, the waste toner container can be detached and emptied or replaced with a new container.
Japanese Laid-Open Patent Application No. 2-293886 (“Patent Document 1”) discloses an image forming apparatus in which an electrostatic latent image formed on the surface of a photosensitive drum as a latent image carrier is developed with a developing unit. A resultant toner image is then transferred from the photosensitive drum to a transfer medium, such as a sheet of paper. Residual toner remaining on the surface of the photosensitive drum after the transfer step is removed by a scraping blade and put into the waste toner container. Further, based on the cumulative count of the number of pixels in output images, the amount of remaining toner on the surface of the photosensitive drum is calculated, and it is determined whether the waste toner container is full based on an accumulated result of such calculations.
Japanese Laid-Open Patent Application No. 2002-169436 (“Patent Document 2”) discloses that the amount of waste toner collected in the waste toner container is estimated from values calculated from print parameters (such as density and the number of pages).
Japanese Laid-Open Patent Application No. 2004-286790 (“Patent Document 3”) discloses an image forming apparatus having a waste toner container for collecting waste toner recovered by a cleaning device. A portion of the side wall of the waste toner container protrudes outward, forming a waste toner detecting space separate from the waste toner container space. The waste toner detecting space is in fluid communication with the waste toner container space so that, when the waste toner container space is full, waste toner can exit the waste toner container space and enter the waste toner detecting space. Two opposite side walls of the waste toner detecting space include light-transmitting areas. A light-emitting portion and a light-receiving portion of an optical sensor unit are disposed opposite to each other on the outer surfaces of these two opposite side walls of the waste toner detecting space. As the waste toner container space is filled with waste toner, the waste toner then begins to enter the toner detecting space. As a result, a ray of light emitted by the light-emitting portion toward the light-receiving portion through the toner detecting space is blocked by the waste toner. In this way, a filled-state of the waste toner container can be detected.
Japanese Laid-Open Patent Application Nos. 3-59585 (“Patent Document 4”) and 2-284190 (“Patent Document 5”) disclose that a detecting unit including a displaceable mechanical sensor is mounted above a waste toner container that is capable of at least partial deformation. As waste toner is collected, the waste toner container inflates and its wall surfaces displace the mechanical sensor, thus indicating that the waste toner container is full.
Japanese Laid-Open Patent Application No. 5-35160 (“Patent Document 6”) discloses that the weight of a waste toner container is measured using a weight measuring mechanism in order to determine whether the waste toner container is full.
Japanese Laid-Open Patent Application No. 8-160822 (“Patent Document 7”) discloses a displacement amount detecting unit mounted on a bottom surface of a waste toner container. The displacement amount detecting unit measures the amount of downward displacement of the toner container relative to a predetermined position as the container's weight increases with increasing amounts of waste toner collected therein. Based on a detection result, whether the waste toner container is full is determined.
The techniques of Patent Documents 1 and 2 do not involve a direct measurement of waste toner in the waste toner container. Thus, the calculation results do not necessarily reflect an accurate amount of waste toner in the waste toner container. For example, the amount of waste toner may actually be much below the full amount when the calculation result indicates that the waste toner container is full. Conversely, the waste toner container may actually be full when the calculation result does not indicate the filled state. In the latter case, if more waste toner is collected, the collected waste toner may flow out of the waste toner container. Thus, whether a certain amount of waste toner has been collected in the waste toner container cannot be accurately determined.
In the case of Patent Document 2, because the monitoring is based on a control routine, the image forming apparatus could be fed with an instruction from a user causing the image forming apparatus into determining that the waste toner container that has been filled has been replaced when in fact it has not been. In this case, the already filled waste toner container may continuously be used, with the resultant overflow of waste toner from the waste toner container, possibly causing contamination of the areas around the apparatus.
In the case of Patent Document 3, waste toner that floats around within the toner casing may attach to the side walls of the waste toner container space. Such attached waste toner may block the ray of light travelling from the light-emitting portion to the light-receiving portion of the optical sensor when the waste toner container space is not yet filled with waste toner, thus resulting in false detection of the filled-up state even before waste toner flows out of the toner container space and enters the toner detecting space.
In Patent Document 4 or 5, where the detector is disposed above the toner container, the detection of the waste toner amount is based on the toner immediately below the detector. However, the toner is not necessarily collected uniformly within the toner container, thereby potentially resulting in false detection of waste toner.
In Patent Document 6 or 7, involving the detection of the weight of the waste toner container, although there is a certain correlation between the waste toner amount and the detected weight, the measurement of waste toner may be inaccurate if some of the toner within the waste toner container is unevenly distributed. In such a case, detection is inaccurate. Further, in Patent Document 7 involving a suction system, a paper container for collecting waste toner is sucked toward the sucking end (such as above), which may prevent an accurate detection of weight. In addition, if the paper container is caught on the casing, the paper container fails to drop, thereby preventing the detection of its weight. In order to prevent such a potential problem, some slack needs to be provided in the space between the paper container and the casing. As a result, the size of the apparatus increases. The use a weight detector also increases cost and size of the apparatus.